Background Apnea of prematurity cannot be reliably measured with current monitoring techniques. Instead, indirect parameters such as oxygen desaturation or bradycardia are captured. We propose a Kalman filter-based detection of respiration activity and hence apnea using multichannel esophageal signals in neonatal intensive care unit patients. Methods We performed a single-center observational study with moderately preterm infants. Commercially available nasogastric feeding tubes containing multiple electrodes were used to capture signals with customized software. Multichannel esophageal raw signals were manually annotated, processed using extended Kalman filter, and compared with standard monitoring data including chest impedance to measure respiration activity. Results Out of a total of 405.4 h captured signals in 13 infants, 100 episodes of drop in oxygen saturation or heart rate were examined. Median (interquartile range) difference in respiratory rate was 0.04 (−2.45 to 1.48)/min between esophageal measurements annotated manually and with Kalman filter and −3.51 (−7.05 to −1.33)/min when compared to standard monitoring, suggesting an underestimation of respiratory rate when using the latter. Conclusions Kalman filter-based estimation of respiratory activity using multichannel esophageal signals is safe and feasible and results in respiratory rate closer to visual annotation than that derived from chest impedance of standard monitoring.

The development of ultrasound over the last 40 years has resulted in a significant improvement in diagnostics across areas of specialization. Findings can be identified and defined with increasing accuracy. An increasing number of congenital heart defects can be diagnosed as early as the 12th-14th gestational week with fetal echocardiography. In addition, the evaluation of detailed anatomical structures and heart function improves prognosis assessment. Important articles in this journal such as the systematic examination of the fetal veins and clarification of the hypoplastic left heart show the new trend toward differential diagnosis. While for example examination of the fetal veins near the heart was initially limited to the evaluation of the inferior and superior vena cava, it is now possible to visualize smaller veins such as pulmonary veins, the coronary sinus, the azygos vein, etc. as a result of the introduction of high-resolution ultrasound equipment. This improves knowledge of both normal and pathological findings. Moreover, experience and the technical advances make it possible to detect much rarer anomalies, to perform better intrauterine monitoring, and to provide better postnatal treatment. The analysis of hypoplastic left heart cases in different subgroups also shows that a ventriculo-coronary connection can be established prenatally and primarily occurs in the anatomical subgroup with mitral stenosis and aortic atresia. Endocardial fibroelastosis is a common concomitant phenomenon. The survival rate between the anatomical subgroups seems comparable and is helpful in prenatal counseling with respect to prognosis. Ultrasound examination in general and in pregnancy in particular requires an increasing level of expertise and is very examiner-dependent. In addition to specialty-specific knowledge, the experience of the examiner plays an important role. The measurement of fetal nuchal translucency (NT) for assessing the risk for chromosomal disorders and as a marker for other congenital anomalies, such as heart defects, can be used as an example of this. The measurement uses standardized image display in an exact sagittal section. NT measurement in the 1/10 millimeter range requires suitable experience and ongoing training with constant supervision. It has been shown that on average at least 50???100 non-diagnostic measurements are needed for qualitatively good distribution of the NT values. The measurements of inexperienced examiners are usually too small 1. Examination duration also experience-dependent. Therefore, the use of so-called sonotrainers in training and advanced training has been a topic of discussion for quite some time. A substantial argument against the use of ultrasound examination phantoms is primarily that image acquisition is performed by an experienced examiner. Since ultrasound is a dynamic examination method, there are limits to the use of static images and acquired 3?D volumes. Although the eye can be trained using these reference images, they do not teach acquisition of the secti...